Forehearth for molten glass and method of controlling the temperature of the glass therein



K. M. HENRY Sept. 26, 1933.

R. s m n N N E R V m W. T A

4 Sheets-Sheet 1 K. M. HENRY Sept. 26, 1933.

FOREHEARTH FOR MOLTEN GLASS AND METHOD OF CONTROLLING THE TEMPERATURE OFTHE GLASS THEREIN Y Flled Aprll 29, 1930 4 Sheets-Sheet 2 mm. om,

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INVENTOR.

BY 7gg@ 74M mwa.

ATTORNEYS.

K. M. HENRY Sept'. 26, 1933.

FOREHEARTH FOR MOLTEN GLASS AND METHOD OF CONTROLLING THE TEMPERATURE OFTHE GLASS THEREIN Filed April 29, 1950 4'Sheets-Sheet 5 Sept. 26, 1933.K. M. HENRY 1,928,288

FOREHEARTH FOR MOLTEN GLASS AND METHOD OF CONTROLLING THE TEMPERATURE OFTHE GLASS THEREIN Filed April 29, 1930 4 Sheets-Sheet 4 mi F11-3512121IN V EN TOR.

ATTORNEYS. l

Patentednsept. 26, 1933 UNITED STATES FOREHEARTH FOR MOLTEN GLASS NDMETHOD OF CONTROLLING THE TEM- PERATURE OF THE GLASS THEREHN Kenneth M.Henry, San Francisco, Calif., asf-s signor, by mesne assignments, toHartford- Empire Company, Hartford, Conn., a corporation of DelawareApplication April 29, 1930. Serial No. @4834i 16 Claims.

This invention relates to a glass furnace and especially to a `boot orfore-hearth therefor and to a method of vcontrolling the temperature ofthe glass therein.

In the production of glassvbottles by the suspended charge feedingprocess, the control of temperature is of greatlmportance. If thetemperature could be accurately and automatically controlled, many ofthe problems incident to the manufacture of bottles would be solved.

In order that the results of improper control may be readily seen,consider the followingz One of the most important features of a bottleis its capacity. During the first stages of manufacture, a charge ofmolten glass is directed into the molds of the blowing machine and sincethe molds are of fixed capacity, it follows that if a given size bottleis made at a certain weight the capacity Will be correct, but anydeviations from that weight will result in incorrect capacities. If thech ge of glass is heavier than the predetermined ure, the resultingbottle will be of short capacity, and conversely, if the charge islight, the bottle will be long in capacity. Furthermore, the diiferencesof capacity tor a given deviation of weight are magnified the smallerthe capacity of the bottle.

The part temperature plays in the process is of great importance. Theiirst point to be noted is that viscosity is directly dependent uponternperature. The lower the temperature the greater the viscosity, thefinal limit being solid glass. On the other hand, viscosity is reducedwith elevations in temperature.' It should be further noted thatwithinthe temperature range at which mol- `ten glass is formed intobottles, the viscosity curve is very steep, which^ naturally means thata slight change in temperature entails a relatively large change inviscosity.

With the foregoing statement of facts in mind, operation of the feedershould be considered. Perhaps the first consideration is the diameter ofthe charge, or gob as it is sometimes called. The diameter of the chargeis to be determined by the size of the opening of the blank mold ontheforming machine, and the charge preferably is just large enough to slipinto the blank mold. Obvious di'iculties are encountered if the chargeis too large and conversely just as serious trouble is encountered if itis'too small. To get the correct diameter, a series of orice rings areused which are attached to the outlet of the feeder and which vary inincrements of 11g of an inch;

'The proper orifice ring is selected and the next step is to get theproper weight of glass. This is (ci. fiaaccomplished by adjusting thelength of the charge. The length is to be determined within fairlynarrow limits by the length of the blank mold. The proper length ofglass is obtained by timing the shears which cut on the stream issuingfrom the orifice. As long as the diameter and length of the chargeremain constant, the Weight of glass will always remain the same, as thespecific gravity of the glass does not change. In the foregoing, it hasbeen assumed that adjustments were madev at a given temperature with theresult that all of the conditions were fulfilled as long as thetemperature remained constant. Suppose the temperature drops a fewdegrees. will not be possible to get the same amount of glass throughthe orifice because the viscosity has A increased, with the result thatthe charge will be shortened and the weight decreased. In practice, thissituation may be met by increasing the interval between the shear cuts,thereby allowing a longer time for the dow of glass through the orice,and thereby obtaining the correct weight of glass in the charge. Sinceall the operations of forming the charge into a bottle are necessarilysynchronized, this change involves a slowing up of production. On theother hand, if the temperature increases, fthe viscosity decreases andthe weight increases with a lengthening and narrowing of the charge. Tocorrect this condition,

the speed is increased. It has been found in practice that all of themoving parts of the feeder and forming machine are inter-related intheir action, and that if adjustments are made for one speed and thisspeed is changed, then the inter-relation is destroyed. The feedershould accordingly be readjusted, but this in practice requiresconsiderable manipulation oi adjusting mechanisms to maintain substantialuniformity of weight of the iinished bottles. The net result is to keepthe average weight of the bottles nearly the same, but structuraldefects are engendered to a greater or less degree, because of thefrequent variations in the shape oi the charge. In order to blow astructurally good bottle, the shape of the charge should never vary andshould closely approximate that of the blank mold. Changes of speed, asnoted above, change the shape of the charge. Y Consequently it isdesirable in order to blow uniformly good bottles that the speed of operation remain constant at that for which all of the adjustments havebeen properly set.

In conjunction with the speeding up or slowing process, the operator ofthe feeder also has some control over the temperature by adjusting theflame which is used to heat the bath of molten Now it glass. This isvdone in the usual manner by admitting more or less fuel by means of theusual valve arrangement. In actual operation, as soon as the operatorsees his glass is too phot, he reduces the flame 'and speeds up themachine.

`Under the newconditions, the glass will gradually become cooler andthen the speed of the machine will be too great. This sequence oi' speedand temperature variation continually goes on as long as the apparatusis in operation.

From the above, the reason for close control of temperature should beapparent.

The object of the present invention is to generstratification of themolten glass into zones or layers of different temperatures; andfurther, to lprovide meansfor automatically maintaining the molten glassat a predetermined temperature at the point of discharge.

The fore-hearth isl shown by way of illustration in the accompanyingdrawings, in which:

Fig. 1 is a central vertical longitudinal section through thefore-hearth and the forward end of the furnace to which it is attached,

Fig. 2 is a cross section taken on line lI-l of Fig. 1, A

Fig. 3 is a cross section taken on line IIL-i1?. of Fig. 1, s

Fig. 4 is a plan view of the fore-hearth partially in section,

Fig. 5 is a diagrammatic view showing the automatic electric controlwhereby the temperature of the molten glass at the point of discharge ismaintained,

Fig. 6 is a diagrammatic view similar to Fig. 5 showing a modified formof electric control,

Fig. rI is an enlarged vertical central section of the cylinder whichcontrols flow of glass to the discharge bowl according to theconstruction shown in Fig. l.

Fig. 8 is a cross section taken on line VIII-VIII of Fig. 7,

Figs. 9 and 10 show a modification of the lower end of the cylinder tothe extent that ports of uneven area are shown,

Figs. 11 and 12 show another modification to the extent that three portsare disclosed through which the molten glass enters the cylinder,

Figs. 13 and 14 disclose still another modification in which a singleport is employed.

Referring to the drawings in detail and particularly Figs. 1 to 4,inclusive, it will be stated that the fore-hearth consists of a built-upcast iron 'trough consisting of a bottom section l, side sections 2, anda Vforward or end section 3. This trough, or boot, as it is commonlycalled, is lined `with a refractory material such as fire clay whichresists the action* of glass and heat. The boot is supported by meansof` rods extending from the buck stays of the melting furnace or bybrackets or the like not here shown. The boot is divided into two zonesor sections generally indicated at B and C which will hereinafter belreferred to as the cooling and heating sections.

' For proper control of the glass discharged from the boot it isnecessary to have the glass behind the heating section Ibelow thetemperature desired in the charge. This is done because it is possibleto obtain more accurate control in heating glass than in cooling it. Asthe glass may bev hotter than desired when entering the boot from theglass furnace, it'is first necessary tov partially cool the molten glassand then to increase the temperature to that required before it isdischarged.I

The cooling section B is lined with a refractory material such asindicated at 4. The rear end, that is, the end nearest the glassfurnace, slopes as indicated at 5 to a submerged throat 6 formed in thebreast wall AY of the furnace. The roof of the cooling section consistsof an arch cover tile 7 and in this cover are placed two surfacecombustion gas burners such as indicated at 8 and 9. These burners areused when the boot is being heated up and also to bring the temperatureof the glass up to a point where it will form a conductor. They are alsoused as an auxiliary source of heat if the temperature of the glass whenentering the boot is so low that the glass will not carry the necessarycurrent to produce a heating effect. In the event of power failure theseburners would also be turned on in order to keep the glass and boot hot.In the tile '7 is formed an opening l0 which is adapted to be connectedwith a stack, not here shown, so as to carry away the combustion gasesto the outside atmosphere. When the' burners are not in operation thisopening is also used as a means for controltroduced which cools theglass. It will be understood that the stack should be provided with adamper so as to regulate the amount of cooling air thus employed. At thefront end of the cooling section is a block 11 whichis used to deflectthe current of glass in an upward direction. The glass entering throughthe throat 6 is usually hotter than desired and it is desirable toprevent glass of too high a temperature from flowing along the bottom ofthe boot to the discharge orifice and thereby causing loss of control.The deflector block 11 directs the moving stream of glass upwardly andto that extent prevents stratification of the molten glass into layersof different n temperature.

Directly above the deiiector block 11 is anwardly into the glass. Thisblock has a threefold'function; first, it directs the upper portion ofthe moving glass stream into the lower portion thereby causing a mixingof the hot and cool glass; secondly, it acts as a shimmer to keep baci:any deleterious matter that may have formed on the surface of the glassor any material previously introduced into the glass which might laterrise to the surface; and third, it separates the upper portion of thecooling zone from the heating zone, thus stopping any air currents whichmight otherwise enter the heating zone. The function of the twodeflector blocks is quite irnportant as it is necessary to have thestream of glass move in the proper channel, their main function beingthat of preventing stratification due to temperature gradients in theglass stream.

The cool glass enters the heating and controlling section indicated atC. This section is divided into three or more zones, each\independentlycontrolled. rThese zones are indicated at ad, 4o and so. zone ao is nextto the cooling section and it is insulated on all sides. This is done toconserve heat and also to stabilize temperature conditions. If moltenglass were introduced into 'a furnace that was perfectly insulated allparts of the glass stream would be at the same temperature. Attempts areaccordingly made to obtain this condition as closely as possible becausel uniformity of temperature throughout the glass that electrodes such asindicated at 14 are placed in the side walls of zone 30. Theseelectrodes are placed in opposition to each other and three setsconsisting of pairs are illustrated in the present instance but it willbe understood that more or less may be used as conditions may demand.`Electrodes in actual use consist of a graphite plate such as indicatedat 15 into which is screwed a graphite rod 16. shrunk around thegraphite rod is a tube 17 which may be made of steel or any other heatresisting metal. The purpose of the tube is to prevent the graphite rod`:from oxidizing and it also acts as a terminal for the electricconnections which are made at `18. The steel tube also gives mechanicalstrength fito the electrode as a whole. The graphite plate '15 is coatedwith an electrode material 19. This coating completely covers thegraphite in order that none of it shall .be exposed to the flowing glassstream. The electrodes arev placed in. re

f cesses formed in the refractory material for the purpe of protectingthe coating 19 from erosion bythe flowing stream of glass. By having theelectrodes disposed in recesses as shown the :laces 19 are maintainedout of contact with the main moving stream, thus prolonging the ille olthe coating. 'I'he space between the cast iron side wall 2 of the bootand the graphite plate its tube i7 is filled with a cement or likematerial to keep the air from oxidizing thegrapliite and the tube.

mitioned above the electrodes i4 are blister traps generally indicatedat 20. When the iur- `nace here shown' was first placed in operationdifiiculty was encountered inV that the glass cf'- charged was found tocontain a streak ci blisters or bubbles. These blisters are bubbles ogas caught in the glass and these constitute a serious defect in anlshed bottle of glassware. lnspec tion showed that the bubbles weregenerated at the electrode faces. .Research determined that the bubbleswere evolved by superheated glass near the faces of the electrodes. Thetempera,-l ture of the electrode faces was approximately 200 F. abovethat of the glass. VThis excessive 'temperature is caused either by acontact resistance or the resistance of the electrode coating. Thehightemperature destroyed the e I equilibrium of the gas producing matterdissolved 'in the glass so that gas was evolved, and, being caught inthe relatively viscous glass, was ren tained as bubbles or blisters. LIt of course would be desirable to prevent the formation ofblisters whenusing this type of electric heating SYStem by having the glass devoid ofany dissolved gas producing matter but at the present time is believednot to be practical.

A remedy accordingly resolves itself into removing the blisters afterthey are formed and thus. preventing them from reaching the gob and thefinished bottle. Thishas been accomplished by use of the blister trapsillustrated. The essential feature of the blister traps is al projectinglip or baille plate such as indicated at 2l. This extends downwardly ntothe flowing glass stream at e. point laterally inward from the associateelectrodes. Each electrode has its own blister trap and all of htheseare interconnected by a channel 22. Openings 23 lead from the channel tothe atmosphere.

When the boot is in operation the blisters travel -upwardly on the facesof the electrodes and into the trap. The glass adjoining the electrodeface has a higher temperature than elsewhere in the glass stream andconsequently has a lower viscosity. Due to this lower viscosity theblisters rise on the electrode faces as they are formed and reach thesurface within the blister trap chamber. Because of the high temperaturedue to the superheated surface the blisters burst and are completelydispersed asthey'reach the' surface, and the gas discharged from thebubbles passes through the openings and then to the atmosphere. If theopenings were not provided gas pressure would develop in the trapchambers and the blisters would then be forced down under the bailleplate 2l and into the main stream of 195 jglass. lf desired, lt lspossible to connect the openings with some source of reduced pressureand thus facilitate the removal of the blisters by allowing the thenrelatively increased pressure within the bubbles to more readily burstthe skin of glass surrounding them. This has, however, not been foundnecessary in practice, since chan-n nel 22 is designed to permit theintroduction ci? burners so that the surface of the glass in the trapsmay be vheated. to such an extent as to lower ,m5 the viscosity ot theglass, thereby permitting the bubbles to freely burst as they reach thesurface.

A brief .description ci the electrodes and the blister traps employed issubmitted in the present n instance as the electrodes and the blistertraps :um disclosed form the subject matters of cci-pendingapplications, Serial No. $80,881. led Sept. it, l93ll, and Serial No.fl5e,504,' led May 3l, i930.

ln connection with zone 3@ of the 'heating sec= non a my be stated metune rco: is formed ci n, m hat slab in which a slot 23u has been cut toallow the introduction el a thermo-couple such as shown at 24, thisthermo-couple forming a ci the control apparatus hereinafter to be demscribed. The slab lormlng the roof is constructed w of goed insulatingmaterial and the center ol the rooi is lower se that it just clears thesurface ci the 'flowing glass stream. This is done to cut down thevolume ol space above the glass and thereby reduces the possibility ofconvection currents which would cause a higher heat loss and might alsocause a tendency to chill the upper surface of the glass. To conserveall of the heat possible and also to maintain all portions of the.

(lll

directed because an openli'ig must e lett the hot gases to pass intozone when gas is in as an auxiliary fuel. f

All that has beensaid of zone 30 applies to zone 40. Zone l0 is,constructed substantially identical to zone 30, the same electrodes areernployed, the same method of insulation, the same type of roof, but inthis instance two slots are formed therein as shown at 26 and 27N topermit insertion of thermo-couples as showin at 28 and 29. Twoelectrodes are employed as shown at Mo. and blister traps are alsoemployed.

Zone 50 is also substantially identical in -con-3 struction with theexception thatfit only employs one pair of electrodes. Also an openingas in dicated at i2 is provided in the roof for the'introu duction of agas burner, this being' employed to heat up the cold bootuntil the glassis sutciently hot to conduct current and it .is also to .be used in caseof emergency due to power shut-downs, etc. Slots32 are formed in theroof and thermoI couples 33, Fig. Il, extend theretlirougl'i.

Between `zones lill and 50 but not completely separating them is placeda cylinder such as in dicated at 34. This cylinder is constructed oiclay or a like refractory material and is provided with one or moreentrance ports as indicated at and 36. The glass ows through these portsand down into a bowl as shown at 37 and finally discharges through theorifice indicated at. i538 where it is cut oli by the shears, not shot/"Q, forni niold charges. The cylinder 34 surrounds a plunger 39 which hasits usual function. The cylinder is open at the top for the inset theplunger and the bottom of the cylinder rests on a supporting ring asindicated at 43, this ring being in turn supported by the insulatinginate= rial shown. The bowl 3*? can be replaced without disturbing thecylinder assembly. It should also be pointed out that the cylinder isnot mede integral with the supporting ring; hence it may be removed orreplaced without much loss of time or Without disturbing any other partof the boot. A clamp, not shown, engages the top of the cylinder andholds it rigidly on the ring 413. The function of the cylinder is toguide the glass where desired in order that the proper temperaturemeasurements may be made. The cylinder is useful in obtaining a goodtemperature wntrol of the glass and'control of the Weight ci tliecharges. Without the use oi a cylinder, there would be diiiiculty inplacing thermo-couple in the flow of glass passing through the bowl. Ethe thermo-couple was placed in the flow was going to the bowl goodresults could loe obtained but due to conditions not under control thetemperature within the mass o glass itself would vary in the verticalplane and possibly in the horizontal. With conditions of that characterthe position of the flow would change as viscosity is directly dependentupon temperature; hence lthe glass will flow most readily where thethermo-couples in the center of ythese ports it is possible toaccurately measure the temperature and thus to maintain it. 'E there isany tero-= perature gradient the extent of it is so sniall thatLoslassen the thermo-couple will correctly record the averagetemperature.

its will be noted from the drawings, see Fig. 2, the cylinder does notcompletely seal oi the sones lo and Sil as a space is left on each sideo the cylinder so that the glass can flow from the section lo into thesection v; hence part of the glass str enters the cylinder through port35 through port 36. The temperature of the glass dowing through the port35 can be controlled in zone 4o and the temperature of the glassentering port 36 can be controlled in zone 5o. permits control of thetemperature distribution because ii the temperature should be lowat theiront of the cylinder it is possible to raise the temperature in zone 50and. this gives a corresponding increase in temperature the glass thatflo-ws into the outer or Jront portion of the discharge bowl and thenceto the outlet. Obviously the same applies to the glass at the baci; or.rearward side l ot the cylinder as suoli gls is controlled in zone andl2 has three similar the perinbery tliereo and the cylinder 34e ci l`Figs. J3 indicated electric controlcircuit is best shown in lflg. 5.will he seen from this figure the elec` trodes arranged in pairs acrossthe boot. The glass between the electrodes acts as the resistor mediumfor generating the heat and comnietes the electric circuit. Electricalenergy is drawn from an alternatore current supply means f n a'transformer Gl. which has a tapped r o2 which furnishes a Variablevoltage noce leads, In this instance one trans- .ed secondary is shownwhich .Jy r all concsin which case all ^e at the same voltage. Anotheralbe to use a transformer for 'each circuit and thus permit voltageregulation in each cone.

Referring to the diagram shown in Fig. 5 the electric control circuitwill be as follows: Electrical energy drawn from an alternating currentsupply 60, through a transformer (ilY which has on the secondary sidevarious voltage taps 62 for the electrodes M of the furnace. The controlcircuit is taken from the primary side of the supply 60. As shown inthis drawing, wire 68 connects with both contacter arms 64 and throughWire 65 with the low side contact 66 of the galvanometer 67. The otherside of this circuit is taken through wire 63 from the supply l0 toresistance 69 and through the resistance and wir@ io enough um sienoia nwhich is con'- as but a single port which is supplies zones o .nectedwith the high side or contact '72 of the lili ` mately controlled asshown in Fig. 5.

67, thereby moving the arm 76 to the contact 66, which closes a circuitfrom the supply through wire 63, resistance 69, wire 70, solenoid 71,contact 74, wire'75, contacts 76 and 66, wire 65, and to the other sideo! .the supply 60 Hy wire 68. 'Ihe solenoid 71 will now close a circuitthrough the electrode relay as current ilows through wire 68, contactor64, contact 81, wire 82, the electrode relay 80 and back to wire 63,through the wire 83. The solenoid 71 will keep energized, even thoughthe arm 76' of the galvanometer 67 leaves the contact 66, as currentwill ilow through wire 68 fromthe supply 60 through contactor arm 64 andacross to the contact 74 through the solenoid 71. wire 70, resistance69, and back to the other side o! the supply 60 by wire B3.

When'the glass is above the required temperature the thermo-couple 77will cause a greater current to be generated in the galvanometer 67,thereby moving the arm 76' to engage the contact 72. The circuit whichhas been( maintained from the supply 60, through solenoid 71, wire 70,and resistance 69 will not be broken b ut will short out the solenoid71. This is accomplished as follows:

From the supply 60 current ilows through wire 68, contact arm 64,contact 74, wire 75, contact 76 of the galvanometer 57, the arm '76',contact 72, wire 73, wire 70, resistance 69 and back to the supply 60 bywire 63. Contacter arms 64 will now disengage the contacts 74 and 8l andthereby break the control circuit through relay 86 and electrodes 14.Then as no current is uowing the glass begins to cool oil. When thetemperature has dropped a few degrees the reverse action takes Vplaceclosing the circuit from the source oi supply to the electrodes 14 witha consequent heating ci' the glass between the electrodes. thetemperature of the glass is automatically conu trolled to apredetermined degree within the range apparatus tory control it isnecessary at all times to have glass entering zone 30 at a temperaturebelow that desired for the temperature setting at that The sameis truewhen zones do and El@ are considered. As the boot is divided into zonesit obvious thot the electrodes in each sone are sepa It has already beenstated that a with variable taps'is employed. This transformer employedas a means to vary and regulate the voltage across the electrodes. Thereason i'or 'varying the voltage follows: Theheeting ol an electriccurrent in a resistor is proportional to the square of the current, theresistance and the time. The resistance of glass varies with the withtemperature it is not always possible to meet all the operatingconditions with one pre-A determined voltage and it is for this reasonthat a tapped transformer is used so as to make it possible to meetvarying conditions. For instance if the wdesired temperature oi' theglass cannot be maintained because at this temperature the glass willnot conduct sumcient current, it is only necessary to change the'taps onthe transformer to increase the voltage, thus forcing more currentthrough the glass and generating a great quantity of heat.

It will be noted thatfin certain zones two r more pairs of'electrodesare employed. When more than one pair is employed it is only necessaryto connect thev pairs in parallel circuit as shown in Fig. 5. In otherwords when two or more pair of electrodes are placed in one zone all areconnected to the same circuit and are controlled and actuated by thethermo-couple andthe mechanism actuated thereby, all pairs being turnedon and of! simultaneously. The' reason for having 'more than. one pairNoi.' electrodes in a zone is to increase the power input in that zone.For instance, if one pair has a given input three pairs will haveapproximately three times the input at the same voltage. The system sofar described is known as an oil and on control as the power is eitherall on or all oli. This is oi' course not the only system that may beemployed. For instance, by referring to Fig. 6, it will be noted that acontrol system is employed wherein, for example, seventy-uve percentofthe power is on all oi' the time and the nal temperature is controlledby adding or cutting oil' an ad ditional twenty-five per-cent oicurrent. In this type oi? system it is necessary to so regulate theconstant input that it will just a conm stant temperature the glasslower than the desired temperature at that point; ii this were not thecase, the temperature would continue to rise and would eventually becomeso high as to result in complete loss ot control.

The control circuit disciesed in Fig. o operates the same as shown in o,but the electrode circuit is slightly dierent. ci ciurent is required,that is, when the molten glass is above the required tempcretine, thether= nio-couple "it generates or causes more current to iioty throughthe gaivanometer causing the contactor am to' to move Contact 72 in.'doing so shorts the control relay solenoid 7l, breaking the circuit tothe electrode relay Elli, and thereby allowing the circuit to theelectrodos to pass tirough the or resistance 90. When the glass is belowthe rcouiredtemperature the thermocoupic "it will generate less current,causlng the arm it of the gulvanometerto engage the contact t6 therebyclosing the contact 64 and in turn completes c. circuit to the electrodorelay solenoid 8u, tm solenoid to when energized will engage contacts:9i sind 92 through the contact crm' e3; thence' the full amount oicurrent will dow through the electrodes 14, the chokeV coil @it beingsnorted. The choke-coilwill oerapproximately seventy-five percent oi'the current to continuously ilow through the elec trodes and the moltenglass, and the thermoacouple together the instrument controlled therebywill automatically make and break a' circuit so as tomaintain theglassat-the desired temperature.

While .certain restores of practical embodi ments of the prent inventionhave been more orless specifically described-herein, I wish it unen asmall amount l ico charge outlet at points spaced around the axial lineof the discharge outlet, separate means for locally heating the glassadjacent to each of said points of passage of glass from the stream tosaid discharge outlet, and means for automatically controlling theoperation of each of said local heating means in accordance with thetemperature of the glass to be heated thereby.

10. A forehearth for molten glass comprising a channel communicating atone end with a source of supply of molten glass and provided adjacent toits opposite end with a downwardly opening passage in its baseterminating in a discharge outlet, a substantially cylindrical verticalbaffle at the upper end of said discharge passage and axially alignedtherewith, said bafile having a plurality of ports in the wall thereofthrough which glass may iiow from said channel into said dischargepassage, temperature responsive means adjacent to each of said ports,and separate heat'- ing means controlled by said temperature responsivemeans for locally heating the glass adjacent to the respective ports.

1l. A forehearth for molten glass comprising a channel communicating atone end with a source of supply of molten glass andv provided adjacentto its opposite end with a downwardly opening passage in its baseterminating in a discharge outlet, a substantially cylindrical Verticalbaie at the upper end of said discharge passage and axially alignedtherewith, said baffle having a plurality of ports in the wall thereofthrough which glass may flow from said channel into said dischargepas/sage, temperature responsive means adjacent to each of said ports,separate heating means controlled by said temperature responsive meansfor locally heating the glass adjacent to the respective ports, saidtemperature responsive means and the heating means controlled therebyacting to bring the temperature of the glass adjacent to each of saidports to a predetermined point Whenever the temperature of such glass issubstantially below that point.

12. That improvement in the art of feeding molten glass through asubmerged discharge outlet for the production of mold charges, whichcomprises flowing molten glass in a stream from a source of supplysuccessively through a cooling chamber and a continuous series ofheating zones to a downwardly opening outlet submerged by glass of thestream, said heating zones and the cooling chamber being separatedagainst heat interchange above thev glass level, cooling the glasspassing through the cooling chamber to a temperaturebelow thetemperature desired for the glass passing through said discharge outlet,and locally heating the glass in each of s aid heating zonesinaccordance with variation of the temperature of such glass from apredetermined temperature. l

13. Glass feeding apparatus comprising a forehearth having a channel forconducting molten glass from a source of supply in a stream toward theouter end of said channel,A said channel having a discharge outlet inits base adjacent to the outer end thereof, means cooperating with theWalls of said channel to provide a cooling charnber in the forehearthadjacent to the source of supply of molten glass, andsuccessive hea-tingzones for the remainder of the length of the fore- 14. Glass feedingmeans comprising a fore-'h hearth having a channel for receiving moltenglass from a source of supply and for conducting such molten glass in astream toward the outer end of said channel, said forehearth having adownwardly directed discharge passage in the base of said channeladjacent to the outer end of the latter and terminating at its lower endin a d'scharge outlet, a cylindrical baille at the upper end of saiddischarge passage and in axial alignment therewith, means providingseparate heating zones at opposite sides of said baille, said baillehaving ports through which glass may pass from sa'd respective heatingzones into the discharge passage, and means individual to each of saidheating zones for locally heating the glass therein adjacent to saidports.

15. Glass feeding means comprising a forehearth having a channel forreceiving molten glass from a source of supply and for conductingsuchmolten glass in a stream toward the outer end of said channel, saidforehearth having a downwardly directed discharge passage in the base ofsaid channel adjacentto the outer end of the latter and terminating atits lower end in a discharge outlet, a cylindrical baille at the upperend of said discharge passage and in axial alignment therewith, meansproviding separate heating zones at opposite sides of said baiile, saidbale having port-s through whch glass may pass from said respectiveheating zones into the discharge passage, thermo-couples in therespective heating zones in position to be affected by the glass passingthrough said portsto said 'discharge passage, and means controlled bysaid thermo-couples for locally heating the glass in said respectiveheating zones.

16. A forehearth for molten glass comprising a channel for receivingglass from a source of supply and forconducting such glass in a streamtoward the outer end of the channel, said forehearth channel havingasubmerged discharge outlet in its base adjacent to the outer endthereof, means providing a series of heating zones through which theglass passes in flowing along said channel to said discharge outlet, apair of spaced electrodes in contact with the glass in each of saidheating zones, thermo-couples individual to each of said heating zonesand in position to be affected bythe temperature of the glass therein,means for supplying electric current to the electrodes in the respectiveheating zones, said electric current supply means being controlled b'yKENNETH M. HENRY.

